PRECISE POINT POSITIONING FOR THE EFFICIENT AND ROBUST ANALYSIS OF GPS DATA FROM LARGE NETWORKS

Networks of dozens to hundreds of permanently operating precision Glob al Positioning System (GPS) receivers are emerging at spatial scales t hat range from 10(0) to 10(3) km. To keep the computational burden ass ociated with the analysis of such data economically feasible, one appr oach is to first determine precise GPS satellite positions and clock c orrections from a globally distributed network of GPS receivers. Then, data from the local network are analyzed by estimating receiver-speci fic parameters with receiver-specific data; satellite parameters are h eld fixed at their values determined in the global solution. This ''pr ecise point positioning'' allows analysis of data from hundreds to tho usands of sites every day with 40-Mflop computers, with results compar able in quality to the simultaneous analysis of all data. The referenc e frames for the global and network solutions can be free of distortio n imposed by erroneous fiducial constraints on any sites.